Phosphorated composite and anode using the same

ABSTRACT

A phosphorated composite capable of electrochemical reversible lithium storage includes a conductive matrix and red phosphorus. The conductive matrix includes a material being selected from the group consisting of conductive polymer and conductive carbonaceous material. A weight percentage of the conductive matrix in the phosphorated composite ranges from about 10% to about 85%. A weight percentage of the red phosphorus in the phosphorated composite ranges from about 15% to about 90%. An anode using the phosphorated composite is also provided.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/720,600, filed on Mar. 9, 2010, and entitled,“PHOSPHORATED COMPOSITE, METHOD FOR MAKING THE SAME, AND LITHIUM-IONBATTERY USING THE SAME,” which claims all benefits accruing under 35U.S.C. §119 from China Patent Application No. 200910080303.8, filed onMar. 18, 2009 in the China Intellectual Property Office.

BACKGROUND

1. Technical Field

The present disclosure relates to a phosphorated composite forelectrochemical reversible lithium storage, method for making the same,and a lithium-ion battery using the same.

2. Description of Related Art

Lithium-ion batteries are used as portable power sources for a widevariety of electronic devices, such as cellular phones, notebookcomputers, and camcorders.

At present, graphite is used as an anode material for lithium-ionbatteries, but higher capacity alternatives are being actively pursued.Among the many possible alternatives, a lot of work has been devoted toSn-based oxide, Si-based composite, transition metal oxide, metalnitride, and metal phosphide systems, due to their ability to reactreversibly with large amounts of Lithium (Li) per formula unit. However,the metal phosphides such as, MnP₄, CoP₃, CuP₂, Cu₃P, FeP₂, Li₂CuP, TiP₂are inorganic composites that have bad cycle performance.

In one article, entitled “Black Phosphorus and its Composite for LithiumRechargeable Batteries” by Hun-Joon Sohn et al., Advanced materials, Vol19, P 2465-2468 (2007), a black P-carbon composite and method for makingthe same is disclosed. The black P-carbon composite includesorthorhombic black phosphorus and carbon modification, and it can beapplied as an anode material for lithium-ion batteries. However, theorthorhombic black phosphorus is expensive and the black P-carboncomposite is hard to make. Thus, the cost of the lithium-ion batteriesis increased.

What is needed, therefore, is to provide a phosphorated anode materialfor lithium-ion batteries which is inexpensive and easy to make.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout several views.

FIG. 1 is a voltage profile of charge/discharge performance of alithium-ion battery according to an embodiment.

FIG. 2 is a voltage profile of charge/discharge performance of alithium-ion battery according to an embodiment.

FIG. 3 is a charge/discharge capacity profile of cycle performances of alithium-ion battery according to an embodiment.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

A phosphorated composite for electrochemical reversible lithium storageof one embodiment includes a conductive matrix and a red phosphorus. Theconductive matrix can be a conductive polymer and/or a conductivecarbonaceous material. The weight percentage of the conductive matrix inthe phosphorated composite ranges from about 10% to about 85%, and theweight percentage of the red phosphorus in the phosphorated compositeranges from about 15% to about 90%.

The conductive polymer can be conjugated conductive polymer. Theconjugated conductive polymer can be a production of a reaction of apolymer under catalysis of the red phosphorus. The reaction can bedehydration, de-amine, dehydrogenation or dehydrohalogenation. Thepolymer can be polypropylene, polyacrylonitrile (PAN), polystyrene,polyethylene oxide, polyvinyl alcohol (PVA), polyvinylidenechloride,polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polyvinylchloride (PVC), poly1,2-chloride ethylene, poly1,2-fluoride ethylene,polymethyl methacrylate, phenolic resin or any suitable polymer whichcan change into conjugated conductive polymer under catalysis of the redphosphorus.

The conductive carbonaceous material can be active carbon, acetyleneblack, conductive graphite, or conductive amorphous carbon. Theconductive amorphous carbon can be made by dehydrogenation of organicmatter such as sugar or cellulose. The dehydrogenation causes theamorphous carbon to be conductive.

A method for making the phosphorated composite can include followingsteps:

step (a), mixing a source material with the red phosphorus to obtain amixture, wherein the weight ratio of the source material to the redphosphorus ranges from about 1:10 to about 5:1;

step (b), drying the mixture in an inert atmosphere or vacuum, whereinthe drying temperature ranges from about 50° C. to about 120° C.;

step (c), heating the mixture in a reacting room filled with an inertatmosphere so that the red phosphorus sublimes, wherein the heatingtemperature ranges from about 250° C. to about 600° C.; and

step (d), cooling the reacting room down.

In step (a), the mixture can be milled by a ball milling process so thatthe source material and the red phosphorus are mixed uniformly. A purityof the red phosphorus is higher than that of industrial grade.

The source material can be the polymer and/or the conductivecarbonaceous material. The polymer and the conductive carbonaceousmaterial can be provided in the form of powder, particles, or fibers.The polymer can be any suitable polymer which can change into conductivepolymer under catalysis of the red phosphorus at the heating temperaturein step (c) and form an in situ composite with the red phosphorus. Thepolymer can be polypropylene, polyacrylonitrile (PAN), polystyrene,polyethylene oxide, polyvinyl alcohol (PVA), polyvinylidenechloride,polyvinylidene fluoride (PDVF), polyvinyl fluoride (PVF), polyvinylchloride (PVC), poly1,2-chloride ethylene, poly1,2-fluoride ethylene,polymethyl methacrylate, or phenolic resin. Also the polymer can be anysuitable organic matter which can change into conductive amorphouscarbon by dehydrogenation at the heating temperature in step (c) andform an in situ composite with the red phosphorus. The organic mattercan be cellulose or sugar. The sugar can be glucose or amylase. Theconductive carbonaceous material can be active carbon, acetylene black,conductive graphite, or conductive amorphous carbon.

In step (b), the mixture can be dried for a period of time from about 1hour to 10 hours so that the water and impurities in the mixture arevaporized. The inert atmosphere can be dry high purity argon gas, dryhigh purity nitrogen gas, or dry high purity helium gas.

In step (c), the mixture can be heated in a sealed reacting room for aperiod of time from about 1 hour to about 48 hours. The reacting roomcan be reacting kettle or tube furnace. When the source material ispolymer, the polymer can change into conductive polymer or conductiveamorphous carbon and absorbs the sublimed red phosphorus to form an insitu composite. When the source material is conductive carbonaceousmaterial, the conductive carbonaceous material can absorb the sublimedred phosphorus to form an in situ composite. The in situ composite isthe phosphorated composite for electrochemical reversible lithiumstorage.

When the phosphorated composite is applied in a lithium-ion battery forelectrochemical reversible lithium storage, the lithium-ion battery caninclude an anode, a cathode, a separator membrane, and an electrolyte.The anode includes the phosphorated composite described above. Thecathode can be made of active material such as lithium cobaltate(LiCoO₂), lithium nickel cobaltate, lithium nickel oxides (LiNiO₂),lithium manganese oxide (LiMnO₂), or lithium iron phosphate (LiFePO₄).The electrolyte generally includes at least one solvent and lithiummetal salt. The lithium metal salt is lithium hexafluorophosphate(LiPF₆). The solvent can be ethylene carbonate, propylene carbonate,dimethly carbonate, diethyl carbonate, dipropyl carbonate, ethyl methylcarbonate etc. Further, an additive can be added into the electrolyte.

Example 1

In example 1, the phosphorated composite of one embodiment is made bythe following steps of:

step (1a), mixing the polyacrylonitrile (PAN, a product of Aldrichcompany) in form of particles with the red phosphorus having a purity ofabout 98% or greater than 98% to obtain a mixture and milling themixture so that the polyacrylonitrile and the red phosphorus are mixeduniformly, wherein the weight ratio of polyacrylonitrile to the redphosphorus is 1:4;

step (1b), drying the mixture in dry high purity nitrogen gas for 6hours, wherein the drying temperature is 70° C.;

step (1c), heating the mixture in a sealed tube furnace filled with dryhigh purity nitrogen gas so that the red phosphorus sublimes, whereinthe heating temperature is 500° C. and heating time is 12 hours; and

step (1d), cooling down the tube furnace to room temperature.

In step (1c), the polyacrylonitrile changes into the conjugatedconductive polymer by dehydrogenation under catalysis of the redphosphorus and absorbs the sublimed red phosphorus to form thephosphorated composite. The phosphorated composite includes theconjugated conductive polymer and the red phosphorus. A measurement ofone embodiment by an element analyzer find that the weight percentage ofthe conjugated conductive polymer in the phosphorated composite is 45%,and the weight percentage of the red phosphorus in the phosphoratedcomposite is 55%.

Furthermore, an embodiment of a lithium-ion battery, comprising of anembodiment of the phosphorated composite of example 1 is provided. Theanode includes an electrode and a nickel foam current collector. Theelectrode includes an embodiment of the phosphorated composite ofexample 1, a bonder, a conductive agent, and a dispersant with a weightratio of 80:10:5:5. The bonder is a poly(tetrafluoroethylene), theconductive agent is acetylene black and conductive graphite with aweight ratio of 1:1, and the dispersant is an ethanol. The cathode is alithium metal sheet. The separator membrane is a CELGARD 2400. Theelectrolyte is 1 mol/L mixture solution of LiPF₆ and a mixture solventof ethylene carbonate, diethyl carbonate and dimethly carbonate with avolume ratio of 1:1:1.

A charge/discharge performance of one embodiment of the lithium-ionbattery is tested. The open circuit voltage of the lithium-ion batteryis 2.7V, and the charge/discharge capacity of the first cycle is 650mAh/g. The charge/discharge capacity is greater than 400 mAh/g after 40cycles.

Example 2

In example 2, the phosphorated composite of one embodiment is made bythe following steps of:

step (2a), mixing the polyvinylidene chloride (PVDC) in form of powderwith the red phosphorus having a purity of about 98% or greater than 98%to obtain a mixture and milling the mixture so that the polyvinylidenechloride and the red phosphorus are mixed uniformly, wherein the weightratio of polyvinylidene chloride to the red phosphorus is 1:2;

step (2b), drying the mixture in dry high purity nitrogen gas for 6hours, wherein the drying temperature is 80° C.;

step (2c), heating the mixture in a sealed tube furnace filled with dryhigh purity nitrogen gas so that the red phosphorus sublimes, whereinthe heating temperature is 450° C. and heating time is 3 hours; and

step (2d), cooling down the tube furnace to room temperature.

In step (2c), the polyvinylidene chloride changes into the conjugatedconductive polymer by dehydrogenation under the catalysis of the redphosphorus and absorbs the sublimed red phosphorus to form thephosphorated composite. The phosphorated composite includes theconjugated conductive polymer and the red phosphorus. A measurement ofone embodiment by an element analyzer find that the weight percentage ofthe conjugated conductive polymer in the phosphorated composite is 60%,and the weight percentage of the red phosphorus in the phosphoratedcomposite is 40%.

Furthermore, an embodiment of a lithium-ion battery, comprising of anembodiment of the phosphorated composite of example 2 is provided. Theelectrode includes an embodiment of the phosphorated composite ofexample 2, a bonder, a conductive agent, and a dispersant with a weightratio of 80:10:5:5. The bonder is a poly(tetrafluoroethylene), theconductive agent is acetylene black and conductive graphite with aweight ratio of 1:1, and the dispersant is an ethanol. The cathode is alithium metal sheet. The separator membrane is a CELGARD 2400. Theelectrolyte is 1 mol/L mixture solution of LiPF₆ and a mixture solventof ethylene carbonate, diethyl carbonate and dimethly carbonate with avolume ratio of 1:1:1

A charge/discharge performance of one embodiment of the lithium-ionbattery is tested. The open circuit voltage of the lithium-ion batteryis 2.7V, and the charge/discharge capacity of the first cycle is 1150mAh/g. The charge/discharge capacity is greater than 300 mAh/g after 40cycles.

Example 3

In example 3, the phosphorated composite of one embodiment is made bythe following steps of:

step (3a), mixing the active carbon in form of powder with the redphosphorus having a purity of about 98% or greater than 98% to obtain amixture and ball milling the mixture so that the active carbon and thered phosphorus are mixed uniformly, wherein the weight ratio of activecarbon to the red phosphorus is 1:1;

step (3b), drying the mixture in dry high purity nitrogen gas for 6hours, wherein the drying temperature is 100° C.;

step (3c), heating the mixture in a sealed reacting kettle filled withdry high purity nitrogen gas so that the red phosphorus sublimes,wherein the heating temperature is 470° C. and heating time is 6 hours;and

step (3d), cooling down the reacting kettle to room temperature.

In step (3c), the active carbon absorbs the sublimed red phosphorus toform the phosphorated composite. The phosphorated composite includes theactive carbon and the red phosphorus. A measurement of one embodiment byan element analyzer find that the weight percentage of the active carbonin the phosphorated composite is 70%, and the weight percentage of thered phosphorus in the phosphorated composite is 30%.

Furthermore, an embodiment of a lithium-ion battery, comprising of anembodiment of the phosphorated composite of example 3 is provided. Theanode includes an electrode and a copper foil current collector. Theelectrode includes an embodiment of the phosphorated composite ofexample 3, a bonder, and a conductive agent with a weight ratio of4:5:5. The bonder is a poly(vinylidene fluoride-hexafluoropropylene)[P(VDF-HFP)], the conductive agent is acetylene black, and thedispersant is an N-methyl pyrrolidone (NMP). The cathode is a lithiummetal sheet. The separator membrane in this embodiment is a CELGARD 2400microporous polypropylene film. The electrolyte is 1 mol/L mixturesolution of LiPF₆ and a mixture solvent of ethylene carbonate, diethylcarbonate and dimethly carbonate with a volume ratio of 1:1:1.

A charge/discharge performance of one embodiment of the lithium-ionbattery is tested. The open circuit voltage of the lithium-ion batteryis about 2.6V, and the charge/discharge capacity of the first cycle is900 mAh/g. The charge/discharge capacity is greater than 500 mAh/g after40 cycles. Referring to FIG. 1, a charge/discharge performance of oneembodiment of the lithium-ion battery in example 3 is shown. Theabscissa axis represents charge/discharge capacity and the ordinate axisrepresents voltage.

Example 4

In example 4, the phosphorated composite of one embodiment is made bythe following steps of:

step (4a), mixing the conductive graphite in form of powder with the redphosphorus having a purity of about 98% or greater than 98% to obtain amixture and ball milling the mixture so that the conductive graphite andthe red phosphorus are mixed uniformly, wherein the weight ratio ofactive carbon to the red phosphorus is 1:1;

step (4b), drying the mixture in dry high purity argon gas for 6 hours,wherein the drying temperature is 100° C.;

step (4c), heating the mixture in a sealed reacting kettle filled withdry high purity argon gas so that the red phosphorus sublimes, whereinthe heating temperature is 600° C. and heating time is 6 hours; and

step (4d), cooling down the reacting kettle to room temperature.

In step (4c), the conductive graphite absorbs the sublimed redphosphorus to form the phosphorated composite. The phosphoratedcomposite includes the conductive graphite and the red phosphorus. Ameasurement of one embodiment by an element analyzer find that theweight percentage of the conductive graphite in the phosphoratedcomposite is 85%, and the weight percentage of the red phosphorus in thephosphorated composite is 15%.

Furthermore, an embodiment of a lithium-ion battery, comprising of anembodiment of the phosphorated composite of example 4 is provided. Theanode includes an electrode and a copper foil current collector. Theelectrode includes an embodiment of the phosphorated composite ofexample 4, and a bonder, a conductive agent with a weight ratio of4:5:5. The bonder is a poly(vinylidene fluoride-hexafluoropropylene)[P(VDF-HFP)], the conductive agent is acetylene black, and thedispersant is an N-methyl pyrrolidone (NMP). The cathode is a lithiummetal sheet. The separator membrane in this embodiment is a CELGARD 2400microporous polypropylene film. The electrolyte is 1 mol/L mixturesolution of LiPF₆ and a mixture solvent of ethylene carbonate, diethylcarbonate and dimethly carbonate with a volume ratio of 1:1:1.

A charge/discharge performance of one embodiment of the lithium-ionbattery is tested. The open circuit voltage of the lithium-ion batteryis 2.7V, and the charge/discharge capacity of the first cycle is 900mAh/g. The charge/discharge capacity is greater than 500 mAh/g after 60cycles. The coulombic efficiency during charge/discharge of thelithium-ion battery is close to 100%. Referring to FIG. 2, acharge/discharge performance of one embodiment of the lithium-ionbattery in example 4 is shown. The abscissa axis representscharge/discharge capacity and the ordinate axis represents voltage.Referring to FIG. 3, cycle performances of one embodiment of thelithium-ion battery in example 4 is shown. The abscissa axis representscycle number and the ordinate axis represents charge/discharge capacity.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Variations may be madeto the embodiments without departing from the spirit of the disclosureas claimed. The above-described embodiments illustrate the disclosurebut do not restrict the scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A phosphorated composite capable ofelectrochemical reversible lithium storage comprising: a conductivecarbonaceous material, and a weight percentage of the conductivecarbonaceous material ranging from about 10% to about 85%; and redphosphorus, and a weight percentage of the red phosphorus ranging fromabout 15% to about 90%.
 2. The phosphorated composite of claim 1,wherein the conductive carbonaceous material is selected from the groupconsisting of active carbon, acetylene black, conductive graphite, andconductive amorphous carbon.
 3. The phosphorated composite of claim 2,wherein the conductive amorphous carbon is made by dehydrogenation ofsugar or cellulose.
 4. The phosphorated composite of claim 1, whereinthe conductive carbonaceous material is an active carbon with a weightpercentage of about 70%, and the weight percentage of the red phosphorusis about 30%.
 5. The phosphorated composite of claim 1, wherein theconductive carbonaceous material is conductive graphite with a weightpercentage of about 85%, and the weight percentage of the red phosphorusis about 15%.
 6. A phosphorated composite capable of electrochemicalreversible lithium storage comprising: a conductive polymer, and aweight percentage of the conductive polymer ranging from about 10% toabout 75% based on the total weight of the phosphorated composite; andred phosphorus, and a weight percentage of the red phosphorus rangingfrom about 25% to about 90% based on the total weight of thephosphorated composite.
 7. The phosphorated composite of claim 6,wherein the conductive polymer is conjugated conductive polymer.
 8. Thephosphorated composite of claim 7, wherein the conjugated conductivepolymer is a product of a reaction of a polymer under catalysis of thered phosphorus; the reaction is dehydration, de-amine, dehydrogenationor dehydrohalogenation.
 9. The phosphorated composite of claim 8,wherein the polymer is selected from the group consisting ofpolypropylene, polyacrylonitrile, polystyrene, polyethylene oxide,polyvinyl alcohol, polyvinylidenechloride, polyvinylidene fluoride,polyvinyl fluoride, polyvinyl chloride, poly1,2-chloride ethylene,poly1,2-fluoride ethylene, polymethyl methacrylate, and phenolic resin.10. The phosphorated composite of claim 6, wherein the conductivepolymer is a pyrolytic polyacrylonitrile with a weight percentage ofabout 45%, and the weight percentage of the red phosphorus is about 55%.11. The phosphorated composite of claim 6, wherein the conductivepolymer is a pyrolytic polyvinylidene chloride with a weight percentageof about 60%, and the weight percentage of the red phosphorus is about40%.
 12. An anode comprising: a phosphorated composite comprising: aconductive matrix, the conductive matrix comprises a material beingselected from the group consisting of conductive polymer and conductivecarbonaceous material, and a weight percentage of the conductive matrixin the phosphorated composite ranging from about 10% to about 85%; andred phosphorus, and a weight percentage of the red phosphorus in thephosphorated composite ranging from about 15% to about 90%.
 13. Theanode of claim 12, wherein the conductive polymer is conjugatedconductive polymer.
 14. The anode of claim 13, wherein the conjugatedconductive polymer is a production of a reaction of a polymer undercatalysis of the red phosphorus; and the reaction is dehydration,de-amine, dehydrogenation or dehydrohalogenation.
 15. The anode of claim14, wherein the polymer is selected from the group consisting ofpolypropylene, polyacrylonitrile, polystyrene, polyethylene oxide,polyvinyl alcohol, polyvinylidenechloride, polyvinylidene fluoride,polyvinyl fluoride, polyvinyl chloride, poly1,2-chloride ethylene,poly1,2-fluoride ethylene, polymethyl methacrylate, and phenolic resin.16. The anode of claim 12, wherein the conductive carbonaceous materialis selected from the group consisting of active carbon, acetylene black,conductive graphite, and conductive amorphous carbon.
 17. The anode ofclaim 12, wherein the conductive matrix is a pyrolytic polyacrylonitrilewith a weight percentage of about 45%, and the weight percentage of thered phosphorus is about 55%.
 18. The anode of claim 12, wherein theconductive matrix is a pyrolytic polyvinylidene chloride with a weightpercentage of about 60%, and the weight percentage of the red phosphorusis about 40%.
 19. The anode of claim 12, wherein the conductive matrixis an active carbon with a weight percentage of about 70%, and theweight percentage of the red phosphorus is about 30%.
 20. The anode ofclaim 12, wherein the conductive matrix is conductive graphite with aweight percentage of about 85%, and the weight percentage of the redphosphorus is about 15%.